This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the specification and claims in this application and is not admitted to be prior art by inclusion in this section.
Various abbreviations that appear in the specification and/or in the drawing figures are defined as below:
AP Access Point
AS Access Stratum
BS Base Station
CN Core Network
CA Carrier Aggregation
DRB Data Radio Bearer
EAP Extensible Authentication Protocol
ECGI E-UTRAN Cell Global Identifier
eNB evolved Node B
EPS Enhanced Packet System
EPC Enhanced Packet Core
E-UTRAN Evolved Universal Terrestrial Radio Access Network
GPRS General Packet Radio Service
GW Gateway
HLR Home Location Register
HSS Home Subscriber Server
IP Internet Protocol
LAN Local Area Network
LTE-LAN/Hi enhanced LTE-based LAN
MME Mobility Management Entity
MSC Mobile Switching Centre
NAS Non Access Stratum
OAM Operations, Administrations and Maintenance
PDU Protocol Data Unit
PDN Packet Data Network
PDCP Packet Data Convergence Protocol
PCI Physical Cell Identifier
RLC Radio Link Control
RNC Radio Network Controller
RRC Radio Resource Control
RRM Radio Resource Management
SRB Signaling Radio Bearer
SN Support Node
UE User Equipment
VLR Visitor Location Register
WAN Wide Area Network
As the number of persons using wireless communication in their daily life keeps increasing, high-speed data transmissions have become highly expected to meet the requirements of a multitude of wireless services. It is known that a LAN system is generally capable of providing relatively high speed data services. How to provide local access with a high speed data rate using a wireless communication system, e.g., an LTE system or an EPS, has become a hot topic in the 3GPP and leads to the emergence of a promising LTE-LAN technique.
An LTE-LAN (also referred to as LTE-Hi) technique is a heterogeneous network technique that can be used in a network consisting of an EPS network comprising macro/micro/pico BSs and a LAN comprising wireless APs. The wireless AP herein is also referred to as a local area BS in the present invention and thus is interchangeably used with the local area BS throughout the present specification. In such a heterogeneous network, a UE may have EPS and LTE-Hi connectivity separately or concurrently. In this manner, the LTE-Hi may provide high performance services for wireless communication users with relatively low costs. For example, the UE may have EPS bearer, offloaded EPS bearer and local autonomous bearer services. For a better understanding of embodiments of the present invention, below is an introduction regarding this heterogeneous network with reference to FIG. 1.
FIG. 1 illustrates an exemplary heterogeneous network 100 including an LTE-LAN, in which exemplary network entities and interfaces between these entities are illustrated and embodiments of the present application can be practiced. As shown in FIG. 1, the LTE-LAN applies a new LTE-like radio interface as a “simplified LTE-Uu” interface between the UE and LTE-LAN AP. Due to requirement for less CN involvement, the LTE-LAN network according to certain embodiments of the present invention supports a “stand-alone” mode where the LTE-LAN network is working autonomously by providing a basic wireless broadband access with UE traffic routing to a local LAN/IP network directly from an LTE-LAN AP and to the Internet via a default GW of this LAN/IP network. This autonomous “stand-alone” mode operation is useful especially in the case where overlaying macro network service (also termed a wide area service relative to a local area service in the present invention) coverage, e.g., provided by an “associated” macro eNB (also termed a wide area BS in the present invention) as illustrated in FIG. 1, is missing or has poor quality or poor capabilities relative to what the service would need. The local LAN transport network may include an ordinary Ethernet-based LAN, i.e. IEEE 802.3 as shown in FIG. 1 or any of its modern extensions like Gigabit-Ethernet. In general, this stand-alone LTE-LAN operation resembles existing Wi-Fi network solutions except that the radio interface is using said simplified LTE-Uu interface with LTE procedures. The LTE local radio would use LTE physical layer or any of its extensions (e.g., LTE-Advanced) and LTE protocols with possible simplifications compared to a WAN. The LTE-LAN may additionally include new features specifically designed for the local wireless access.
For the autonomous stand-alone mode operation as discussed above, the LTE-LAN network provides means for UE authentication and authorization to use services provided by the LTE-LAN network. This may be implemented by using similar methods as applied in WLAN (IEEE 802.11i) but modified to carry the authentication protocol messages, e.g. EAP encapsulated into LTE Uu RRC messages. In FIG. 1, there is shown an optional local authentication server that may be a RADIUS server or a diameter server like the one used in enterprise networks.
FIG. 2 illustrates a vertical RRC protocol stack for the LTE-Hi as illustrated in FIG. 1. For a concise purpose, some protocol layers that are necessary but not closely relevant to the embodiments of the present invention are omitted in this example protocol stack. In the illustrated protocol stack, communication entities, such as the UE, the LTE-Hi AP, the associated macro eNB, and the MME, may communicate with one another over corresponding peer layers. Also seen in the protocol stack are EPS RRC and PDCP entities at the associated macro eNB being located on top of local RRC and PDCP entities, i.e., RRC* and PDCP* as identified at the UE and LTE-Hi AP. This protocol arrangement is in a NAS-like style and enables flexible and independent implementation of the local RRC and PDCP functions. Under this protocol arrangement, in order to reuse the current EPS security mechanism, a straightforward approach is to treat the LTE-Hi AP as illustrated in FIGS. 1 and 2 as a subsystem of a macro eNB network (e.g., an EPS network, which is a specific type of a wide area network according to embodiments of the present invention) and inter-AP (a source AP and a target AP) mobility would necessarily involve EPS security key's change based on some parameters (e.g., PCI and a certain frequency) of the target AP. This means that even for UE's inter-AP mobility with a direct X2 interface between APs, the associated macro eNB is involved in the handover preparation and execution.
For an easy and purposeful discussion, reference will be made to FIG. 3 which schematically illustrates a simplified network architecture 300 in which the embodiments of the present invention may be practiced. As illustrated in FIG. 3, the network architecture 300 includes a UE which is being served by a source AP, a potential target AP1, a potential target AP2, and an associated macro eNB (i.e., the wide area BS), wherein the source AP, the potential target AP1 and the potential target AP2 are interconnected via X2 interfaces and each connected with the associated macro eNB via S1′ (i.e., simplified S1) interfaces. When the UE becomes increasingly remote from the source AP and move towards the target AP1 or AP2, this inter-AP mobility may bring about some potential problems.
First, the wide area service (e.g., EPS service) may be lost during the handover between APs. In particular, for a single radio mode UE currently working under the coverage of the source AP with both ongoing local service and EPS service, a neighbor AP, e.g. target AP1, is reported to the network side during UE's mobility. For a local service handover, the X2 interface based handover between APs is suitable due to lack of involvement of the macro eNB. In contrast, for an EPS service handover, an S1′ interface based handover may be more preferred as the macro eNB is responsible for managing EPS bearers and some EPS security keys whenever update is needed. Normally, the X2 based handover preparation would be faster than the S1′ based handover due to shorter latency and route. Thus, it is very likely that the source AP receives the handover ACK (i.e., handover command) from the target AP for the local service handover before any response from the associated macro eNB for the EPS service handover. At this point, if the source AP chooses to forward the handover command to the UE, then the subsequent handover command for the EPS service issued by the associated macro eNB via the source AP might not reach the UE since the UE, at this moment, has already been handed over to the target AP. In this case, the EPS service would definitely be lost during UE's mobility.
Second, a handover collision may arise between the EPS service and local service during the inter-AP handover. In particular, for two RRC modes in the LTE-LAN, the EPS RRC is in charge of EPS bearer's management including configuration and mobility control, and the local RRC is for local bearer's management. These two RRC functions are decoupled in most cases to enable more flexible LAN design and implementation. Since the multi-cell handover preparation feature has already been supported in the existing standard and product, it is likely that the independent EPS RRC and local RRC controls end up with different target cells handover decision. Thus, the handover collision needs to be resolved since the UE can only be handed over to only one target cell.